As a method for producing a color filter used in a liquid crystal display device, there are known methods for applying a color using pigment, such as a pigment dispersing method or an electrodeposition method, and for applying a color(s) using dye, such as a dyeing method or a dye dissolution method. Usually, a color filter layer consists or three primary colors, red, green and blue. The colored patterns of the color filter layer having a coating thickness of 1 to 2 .mu.m are formed in a mosaic pattern or in a stripe pattern.
In general, it is said that although dye is superior in transparency and purity of color and more abundant in kind compared with pigment, the former is inferior in light resistance to the latter. Also, it is known that color material such as pigment and dye is usually susceptible to fading on exposure to light due to oxidation and especially due to singlet oxygen produced by light (some colorant acts as a catalyst in this reaction)
However, the abovementioned general knowledge about fading is not applicable to the color filter used in a liquid crystal display device because such a color filter is panelized and then assembled in the display device and therefore, the inside of the panel is completely isolated From air, thus prohibiting progress of fading due to oxidation. This can easily be understood from the following facts. When, for example, a phthalocyanine-based dye, which is widely known as having a good light resistance, is used as a colorant for a color filter used in a liquid crystal display device, the dye is readily changed in color in spite of the fact that it is used in a circumstance completely isolated from air. In contrast, when a xanthene-based dye such as rhodamine, which is generally considered as being inferior in light resistance, is used as a colorant for a color filter, the dye is not readily changed in color and it can exhibit a strong light resistance in spite of the fact that it is used in the same circumstance where the dye is completely isolated from air.
Heretofore, color filters used in liquid crystal display devices have been manufactured by properly selecting dyes having a good light resistance based on experiences, utilizing the aforementioned special circumstance.
Recently, among liquid crystal display devices, the reflection type liquid crystal display devices drew much attention in order to obtain portable terminal devices with a color display capability. Since the reflection type liquid crystal display devices can be advantageously used as portable display devices in view of reduced consumption of power because the reflection type liquid crystal devices utilize natural light surrounding the devices instead of using a back light.
As one way for providing a color display capability to the reflection type liquid crystal display devices, a color filter is used. Such reflection type liquid crystal display devices themselves include, as discussed, for example, in Japanese Patent Unexamined Publication (KOKAI) No. Hei 8-304816 or Hei 9-68608, a color filter disposed on a surface of a liquid crystal layer as an optical shutter and adapted to provide a color display capability, and a reflective layer disposed on the other surface and having a light reflective function. In this method using a color filter, a wider color displaying range can be enjoyed easily by as making the background color paper white. Therefore, this method is advantageous compared with others using no color filter.
Incidentally, with respect to a color filter used in a reflection type liquid crystal display device, usually, a technique of manufacture following the method of manufacturing a transmission type color filter is solely used. However, it is demanded for the reflection type liquid crystal display device that brightness as much bright as possible ((i.e., thin in color) is ensured as a color filter because an incident light coming from the surroundings of the display device passes (penetrates) through the color filter twice and in addition, a color reproduction range is as large as possible. Also, besides the primary colors red (R), green (G) and blue (B), complementary colors yellow (Y), cyan (C) and magenta (M) are used. The color filter itself using dye is known per se. It is also known that the filter using dye is good in light resistance (for example, see U.S. Pat. No. 4,837,098).